The store spread across the country like wildfire. But its first full-stocked grocery didn't open until 1988

AP

The first Wal-Mart Supercenters opened in 1988 which combined the discount outlets and grocery stores.

There had been complaints about the Hypermarts not providing a fully-stocked grocery offering. Wal-Mart attacked these issues by opening five supercenters with better-stocked grocery sections. The Hypermart format was eventually phased out when the supercenters took off.

Hundreds of supercenters were opened during the 1990s under the direction of David D. Glass who took over as CEO and president in 1988.

Wal-Mart's grocery category is the largest of the company's six merchandise units. The grocery business includes meat, produce, household chemicals and pet supplies.

Walmart kicked ass during two successive recessions

Wal-Mart thrived during the latest recession because of its prices for food, pharmacy and household goods and renovation made it more appealing to its core customer base, households with under $70,000.

As part of its renovation it made the store look cleaner by widening aisles, eliminating clutter, improving lighting and lowering shelves.

Now it's $112 billion ahead of its second-closest competitor for total sales

AP

According to the report in terms of total sales of supermarket items for 2010 stores such as Kroger, Safeway and Cosco are distantly trailing Wal-Mart.

It had $188.3 billion in sales in its 3,599 supermarket stores. Kroger came in second with $76.2 billion followed by Safeway with $41 billion.

Wal-Mart holds a top spot in more markets than any other supermarket

It has opened 94 stores since 2009 while Kroger closed six and Safeway shut down 25.

The giant is cheaper than other grocery stores by an average of $3.02

Wal-Mart's prices have stayed below the competition since January of 2009.

In the same 31-item basket tested by all the stores in the study, Wal-Mart's items priced lower on 68% of the items.

It has an average price of $3.02 and a total basket averaging $93.67 for January 2011, according to JPMorgan's Charles Grom. Whole Foods was the most expensive with an average price of $4.06 and total basket of $125.71 on average in January 2010.

Other stores such as SuperValu have trouble with pricing strategy. It is targeting regular prices that are 10-15% above Wal-Mart.